Influence of cold acclimation on membrane injury in frozen plant tissue

Cold-acclimated twigs of Amelanchier alnifolia Nutt. released less HCN at −4.5 C than nonacclimated twigs following slow freezing to −25 C or rapid freezing to −78 C. Cold-acclimated twigs frozen slowly to −25 C released more HCN than cold-acclimated twigs frozen only to −4.5 C. Cold-acclimated twigs frozen slowly to −25 C and then rapidly to −78 C released less HCN at −4.5 C than cold-acclimated twigs frozen rapidly to −78 C. In general, K⁺ efflux and the inability to reduce triphenyl tetrazolium chloride following freezing and thawing paralleled HCN release at −4.5 C. Because low K⁺ efflux and high triphenyl tetrazolium chloride reduction are known to depend upon membrane integrity, the increased K⁺ efflux and the decreased triphenyl tetrazolium chloride reduction following freezing and thawing provide indirect evidence that HCN release at −4.5 C is a measure of membrane damage in frozen cells.